Religion is entered as an attribute. Besides all attributes built into GEDCOM 5.5.1 (and supported in GEDitCOM iI), you can lways attach a “Generic Attribute”. This creates a FACT tag (in GEDCOM 5.5.1). You use the field to enter the fact, which here might be a membership number. Then click the “i” icon for attribute details. You can enter all that is known. Most importantly, change the “Type” to describe the attribute such as name of the fraternal organization or labor union.
If you will use the same custom attribute frequently, you can build it into any browser style. Open the browser style in the GEDitCOM Editor and then:
1. Expand “Properties” section and click on “INDIEvents”
2. Click “+” icon and set key to FACT# where # makes it a unique key (like FACT1, FACT2, etc.)
3. Set “Value” to name of the fact (like “Elks Lodge”, “Steelworkers Union”, or whatever you will commonly need)
4. Save and reload that format in GEDitCOM II
When you attach an event or attribute, that new fact can be selected from the list and Type will be set to the “Value” you provided.
I just noticed that GEDitCOM Editor help does not mention this as an option for FACTs, but it has been available since GEDitCOM II switched to GEDCOM 5.5.1. I will update the help.